<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>10. 检测是否是2到4位汉字</title>
</head>
<body>
    <script>
        let str = "我爱中国";
        let reg = /^[\u4e00-\u9fa5]{2,4}$/;
        console.log(reg.test(str));
    </script>
</body>
</html>